Removed deprecated command from glance cli

Member-add is no longer a command in python-glanceclient and
should be removed since it has been deprecated. We are removing
all the deprecated glance client commands in this patch
https://review.openstack.org/#/c/98862/.

Change-Id: I69f7ca5ca0e1d9505334f081b7de1f43e6b2f86c
(cherry picked from commit 17889d08bd340a42ea578801414051630c88ee36)